I am not sure but is it right in my eyes that the Player and NPC characters have unique colour codes on their uniforms?
When I am at the tailor trying to figure out what gold/ocre tone the Engineer Corps has, I can't find the right one.
Part of your problem might have to do with the ambient lighting in where ever you are looking at the particular NPC. different areas have different ambient lights and can cause the colors to look different. Most Tailors, i have noticed do not use the best lighting for how the uniform looks so you can get a discrepancy on what the uniform looks like, even if you are using the correct colors.
Someone linked Blackavaar's guide. That is a great source for both canon and in-game uniform colors.